1. Field of the Invention
The present invention relates generally to marine automatic steering apparatus and, more particularly, is directed to an automatic steering apparatus for ships provided with an indicator which indicates a course deviation for the aid of steering the ships.
2. Description of the Prior Art
FIG. 1A shows an example of a pilot head mechanism which is a main portion of a man-machine interface of a prior art marine automatic steering apparatus. This pilot head mechanism is disposed at the central portion of the panel of the marine automatic steering apparatus though not shown. FIG. 1B is a block diagram showing a system of the apparatus shown in FIG. 1A.
In FIGS. 1A and 1B, reference numeral 1 designates a course setting knob, reference numeral 2 designates a gear mechanism which is ganged with the course setting knob 1, and reference numeral 3 designates a needle or pointer which indicates the course set by the course setting knob 1 in cooperation with a repeater card which will be described later. Reference numeral 4 designates a set course delivered from the gear mechanism 2, and reference numeral 5 designates generally a course setting mechanism including the elements 1, 2 and 3 mentioned above. Reference numeral 6 designates a repeater motor, reference numeral 7 designates a gear which transmits the output of the repeater motor 6, reference numeral 8 designates a repeater card that is rotated by the gear 7, reference numeral 9 designates a lubber line, reference numeral 10 designates a ship's heading produced from the gear 7, and reference numeral 11 designates generally a steering repeater including the above mentioned respective elements 6, 7 and 8. Reference numeral 12 designates a difference between the set course 4 and the ship's heading 10, that is, a course deviation, and reference numeral 13 designates a course deviation mechanism which produces the above mentioned course deviation 12.
In the thus constructed prior art automatic steering apparatus, under the automatic steering mode for automatically keeping the ship's heading at a desired course, the main function and role are played by the pilot head mechanism which is formed of the course setting mechanism 5 in which the course setting pointer 3 is set at a desired azimuth scale through the gear 2 by rotating the course setting knob 1, the steering repeater 11 in which the rotation of the repeater motor 6 such as a step motor or a synchro motor driven by an azimuth sensor (not shown) such as a gyro compass and so on is transmitted through the gear 7 to the repeater card 8 such that the ship's heading signal 10 is indicated as the scale on the repeater card 8 coincident with the lubber line 9 fixed to the bow direction of the ship's hull and the course deviation mechanism 13 supplied with the set course 4 from the course setting mechanism 5 and the ship's heading 10 from the steering repeater 11 and which generates the difference therebetween, that is, the course deviation 12.
The above mentioned mechanisms 5, 11 and 13 are formed as mechanical types so that the assembly and the adjustment thereof are very difficult and troublesome. Of course, they are very expensive from a money standpoint and in addition, they are worn and have got more decrepits so that the maintenance thereof becomes cumbersome. Particularly, the decrepit mechanism considerably deteriorates the course keeping quality or ability on the automatic steering mode.
On the other hand, in the apparatus shown in FIG. 1, the scale of the repeater card 8 indicated by the lubber line 9 indicates the ship's heading, the scale of the repeater card 8 indicated by the pointer 3 indicates the set course and the difference between both the scales, that is, the angle between the pointer 3 and the lubber line 9 indicates the course deviation 12 so that the direction of the course deviation 12 and the magnitude thereof can be roughly understood at first sight.
When electronic technique, which is rapidly advanced recently, is utilized in order to solve the afore-mentioned problems, the above mentioned advantages of the prior art automatic steering apparatus are lost. In other words, if the desired course is set in a digital fashion and the ship's heading is digitally indicated by numerals, although the above mentioned complicated and expensive mechanisms become unnecessary, the magnitude of the course deviation can not be perceived immediately and the understanding of the automatic steering property and the checking of the yawing (yawing in the bow) become difficult. In order to carry out an automatic course change so as to change a desired course, when the set course is reset, the direction (polarity) of the course deviation can not be perceived immediately. This brings about the defect in the operation of the apparatus and the operator can not help but feel uneasiness and a burden psycologically. In addition, there is then a problem from a safety operation standpoint.
On the other hand, the indication system formed of the lubber line 9 of the steering repeater 11 and the repeater card 8 which can indicate the ship's heading immediately is excellent from a human engineering standpoint. Particularly in a manual steering mode in which the operator or helmsman steers a steering wheel, this indication system can not be omitted from a steering standpoint, while the digital indication system causes problems from operation and safety standpoint.